The present invention relates to improvements in trailer bumper hitch apparatus; and more particularly, the improvements relate to extendable hitches such as that disclosed in the Antici U.S. Pat. No. 3,140,881, issued July 14, 1964, and the Dietrich, Sr. U.S. Pat. No. 4,265,465, issued May 5, 1981. These patents disclose a trailer hitch which makes it easier to attach a trailer hitch drawbar to a trailer by utilizing two release mechanisms. One of these release mechanisms, when actuated, permits the drawbar to be moved longitudinally toward the rear so that it can be aligned with the hitch of the trailer. The other release mechanism permits the drawbar to be swung laterally in a rearwardly extended position--thus greatly increasing the range over which the drawbar can be connected to the trailer without moving either vehicle. These trailer hitches have the further advantage that no special maneuvering is required to reset both release mechanisms. When the towing vehicle turns, the release mechanism is reset, and when the towing vehicle brakes or slows down, the longitudinal release mechanisms operate independently of each other. These trailer hitches, and other similar extendable trailer hitches, have provided substantial convenience to users, particularly in the agricultural industry where trailer loads may be quite heavy, and the terrain on which it is desired to hitch a trailer to the towing vehicle may be rough or uneven.
Bumper hitches for trucks and the like are typically bolted to a short piece of the truck frame behind the rear spring shackle. The hitch frame extends rearwardly from its mounting on the truck frame to a drawbar or ball mount for securing the tongue of a trailer. No provision is made to reduce the leverage exerted on the bolts attaching the bumper to the truck frame due to the weight of the trailer on the drawbar or ball mount. Eventually, the trailer hitch will become canted towards the rear as the torque on the bolts attaching the bumper hitch to the truck frame elongate the holes through which they are secured. A common solution to the problem has been to weld the trailer hitch frame to the truck frame in front of the main rear brackets utilizing additional steel sheet supports or the like. However, these welds are usually less than ideal because the operator is welding on vertical surfaces beneath his vehicle, often in close proximity to vehicle fuel tanks. If the bumper is to be removed to transfer to a new truck it requires a torch to remove the bumper. Further the welds do not allow the hitch to be suspended at various positions beneath the vehicle frame or to be adjusted for wear in the rear bracket bolts.
The torque force exerted upon the bumper hitch frame and the vehicle frame is further accentuated during the use of extendable bumper hitch systems. Such systems generally have an extendable drawbar or the like capable of telescoping out 6 to 15 inches. When heavy drawbar loads are exerted on an extended drawbar the cantilever load on the end of the truck frame is magnified greatly.
Further, todays demands for greater fuel economy have produced lighter trucks with weaker frames. Such trucks are not able to withstand the cantilever forces exerted on a hitch without a means for distributing such a load over a greater portion of the truck frame.